In October 2015,[62] a development governance was proposed as Ethereum Improvement Proposal, aka EIP, standardized on EIP-1.[63] The core development group and community were to gain consensus by a process regulated EIP. A few notable decisions were made in the process of EIP, such as EIP-160 (EXP cost increase caused by Spurious Dragon Hardfork)[64] and EIP-20 (ERC-20 Token Standard).[65] In January 2018, the EIP process was finalized and published as EIP-1 status turned "active".[62] Alongside ERC-20, notable EIPs to have become finalised token standards include ERC-721[66] (enabling the creation of non-fungible tokens, as used in Cryptokitties) and as of June 2019, ERC-1155 [67] (enabling the creation of both fungible and non-fungible tokens within a single smart contract with reduced gas costs).
In 2016 a decentralized autonomous organization called The DAO, a set of smart contracts developed on the platform, raised a record US$150 million in a crowdsale to fund the project.[25] The DAO was exploited in June when US$50 million in ether were taken by an unknown hacker.[26][27] The event sparked a debate in the crypto-community about whether Ethereum should perform a contentious "hard fork" to reappropriate the affected funds.[28] As a result of the dispute, the network split in two. Ethereum (the subject of this article) continued on the forked blockchain, while Ethereum Classic continued on the original blockchain.[29] The hard fork created a rivalry between the two networks.
Lightweight clients consult full clients to send and receive transactions without requiring a local copy of the entire blockchain (see simplified payment verification – SPV). This makes lightweight clients much faster to set up and allows them to be used on low-power, low-bandwidth devices such as smartphones. When using a lightweight wallet, however, the user must trust the server to a certain degree, as it can report faulty values back to the user. Lightweight clients follow the longest blockchain and do not ensure it is valid, requiring trust in miners.[101]
A lot of concerns have been raised regarding cryptocurrencies’ decentralized nature and their ability to be used almost completely anonymously. The authorities all over the world are worried about the cryptocurrencies’ appeal to the traders of illegal goods and services. Moreover, they are worried about their use in money laundering and tax evasion schemes.

Bitcoin has been criticized for the amount of electricity consumed by mining. As of 2015, The Economist estimated that even if all miners used modern facilities, the combined electricity consumption would be 166.7 megawatts (1.46 terawatt-hours per year).[142] At the end of 2017, the global bitcoin mining activity was estimated to consume between one and four gigawatts of electricity.[211] According to Politico, even the high-end estimates of bitcoin's total consumption levels amount to only about 6% of the total power consumed by the global banking sector, and even if bitcoin's consumption levels increased 100 fold from today's levels, bitcoin's consumption would still only amount to about 2% of global power consumption.[212]
Physical wallets store the credentials necessary to spend bitcoins offline and can be as simple as a paper printout of the private key:[7]:ch. 10 a paper wallet. A paper wallet is created with a keypair generated on a computer with no internet connection; the private key is written or printed onto the paper[h] and then erased from the computer. The paper wallet can then be stored in a safe physical location for later retrieval. Bitcoins stored using a paper wallet are said to be in cold storage.[104]:39 In a 2014 interview, QuadrigaCX founder Gerald Cotten explained that the company stored customer funds on paper wallets in safe deposit boxes: "So we just send money to them, we don’t need to go back to the bank every time we want to put money into it. We just send money from our Bitcoin app directly to those paper wallets, and keep it safe that way."[105]
Ethereum's blockchain uses Merkle trees, for security reasons, to improve scalability, and to optimize transaction hashing.[60] As with any Merkle tree implementation, it allows for storage savings, set membership proofs (called "Merkle proofs"), and light client synchronization. The Ethereum network has at times faced congestion problems, for example, congestion occurred during late 2017 in relation to Cryptokitties.[61]
In February 2014 the world's largest bitcoin exchange, Mt. Gox, declared bankruptcy. The company stated that it had lost nearly $473 million of their customers' bitcoins likely due to theft. This was equivalent to approximately 750,000 bitcoins, or about 7% of all the bitcoins in existence. The price of a bitcoin fell from a high of about $1,160 in December to under $400 in February.[67]
In 2016 a decentralized autonomous organization called The DAO, a set of smart contracts developed on the platform, raised a record US$150 million in a crowdsale to fund the project.[25] The DAO was exploited in June when US$50 million in ether were taken by an unknown hacker.[26][27] The event sparked a debate in the crypto-community about whether Ethereum should perform a contentious "hard fork" to reappropriate the affected funds.[28] As a result of the dispute, the network split in two. Ethereum (the subject of this article) continued on the forked blockchain, while Ethereum Classic continued on the original blockchain.[29] The hard fork created a rivalry between the two networks.
According to The New York Times, libertarians and anarchists were attracted to the idea. Early bitcoin supporter Roger Ver said: "At first, almost everyone who got involved did so for philosophical reasons. We saw bitcoin as a great idea, as a way to separate money from the state."[131] The Economist describes bitcoin as "a techno-anarchist project to create an online version of cash, a way for people to transact without the possibility of interference from malicious governments or banks".[134] Economist Paul Krugman argues that cryptocurrencies like bitcoin are "something of a cult" based in "paranoid fantasies" of government power.[135]
Ether is a token whose blockchain is generated by the Ethereum platform. Ether can be transferred between accounts and used to compensate participant mining nodes for computations performed.[3] Ethereum provides a decentralized virtual machine, the Ethereum Virtual Machine (EVM), which can execute scripts using an international network of public nodes.[4] The virtual machine's instruction set, in contrast to others like Bitcoin Script, is thought to be Turing-complete. "Gas", an internal transaction pricing mechanism, is used to mitigate spam and allocate resources on the network.[4]
Blockchain analysts estimate that Nakamoto had mined about one million bitcoins[32] before disappearing in 2010, when he handed the network alert key and control of the code repository over to Gavin Andresen. Andresen later became lead developer at the Bitcoin Foundation.[33][34] Andresen then sought to decentralize control. This left opportunity for controversy to develop over the future development path of bitcoin, in contrast to the perceived authority of Nakamoto's contributions.[35][34]
×